This investigtion will attempt to determine how immunological abnormalities play a part in the pathogenesis of juvenile rheumatoid arthritis (JRA). Our previous work has shown that JRA patients frequently have immune complexes (IC) which contain classic or hidden 19S IgM rheumatoid factor (RF) and IgG. Futhermore, hidden RF presence correlates directly with disease activity. Thus, it appears likely that complete characterization of these IC will shed some light on the pathophysiology of JRA. We will attempt isolation of IC in the serum and synovial fluid (SF) from JRA patients by 6 physical and immunochemical procedures which are currently under development: (1) an anti-human IgM affinity column to isolate IgM-containing IC, (2) Clq solid-phase and solid-phase anti-C3 acting as matrices, (3) polyethylene glycol (PEG) precipitation and acid-treatment to separate the IC, (4) PEG-acid treatment and subsequent separation of fractions by incubation with protein Staph A bound to Sepharose CL-4B, and (5) Sephacryl S-300 column. IC molecular size will be determined by (6) sucrose density gradient ultracentrifugation. Isolated IC will be analyzed biochemically in addition to 19S IgM RF, hidden 19S IgM RF, and IgG for the possible presence of membrane glycoproteins, peptidoglycan-polysaccharides, and collagen content and immunochemically for possible antibody activities against nuclear material and ds-DNA. A second line of investigation addresses the cellular abnormalities in JRA patients. Cellular studies will be performed to evaluate if hidden 19S IgM RF has any anti-lymphocyte activity. JRA patients' plasma and SF will be evaluated for T-cell subsets and plaque forming cells. JRA lymphocytes in culture will also be stimulated with EB virus to evaluate RF and immunoglobulin release. These methods may lead to evaluating the humoral and cellular mediated abnormalities in JRA. The ability to define the antibody and antigen in JRA is important. Being able to define the antigen or its by-product would aid greatly in defining the disease, determine therapy, and provide possible future research aims in JRA. The ability to define T-cell abnormalities or lymphocytes actively secreting RF that may play a role in pathogenetic mechanism of JRA also would lead to in vitro evaluations of therapeutic modalities.